Acid activated clay



Patented Aug. 24, 1937 PATENT OFFICE ACID ACTIVATED CLAY Ernest W.Zublin, Fort Worth, Tex" assignor to Texas Pacific Coal & Oil 00., FortWorth, Ten,

a corporation of Texas Application December 8, 1932,

No Drawing.

Serial No. 646,303

17 Claims.

sites, etc., and related clays. Such clays for activation are treatedwith varying amounts of strong mineral acids, usually sulphuric orhydrochloric acids, washed with water and, in accordance with priorpractice, are then either mixed with oil while in pulp form, or firstdried and then mixed with the oil. In either case the mixture of oil andclay is generally heated to temperatures ranging from 250 to 700 F.,depending upon the nature of the oil as well as that of the clay inorder to accomplish the transfer of coloring matter from the'oil to theclay. If the clay is used in pulp form, then during the heating, wateris evaporated and causes considerable and troublesome foaming. Specialand expensive equipment is necessary and has been used to obviate thisfoaming. If the clay is first dried by prior methods to a water content.at which it no longer will cause excessive foaming when heated to atemperature above 250 F. in admixture with oils, drying causes it tolose part of its decolorlzing efficiency, the efllciency in the presentinstance being measured as the relation of the weight of clay requiredon a dry basis to produce an oil of a color identical with. thatproduced with a weight of some standard clay used in 10% by weightproportion to the oil.

Accordingly, a principal object of the present invention is to provide aprocess for drying acidactivated clays which preserves their originaldecolorizing efllclency.

Another object is to provide a process capable of increasing thedecolorizing efiiciency of already dried acid-activated clays where thedrying has decreased their efflciency.

A further object of the invention is to provide moisture is plottedagainst efliciency on semilog-arithmic paper a straight line results onthe graph. See, for example, the article by E. R. Lederer and E. W.Zublin, in the National Petroleum News of August 31, 1932, page 27, Themathematical formula for the moisture efllciency relation is I E=104-l0(1.64-.015 M) where E=Efllciency M=Moisture The theory proposedconcerning this relation is that the most active ingredients ofactivated clays are primary aluminum salts of poly-silicic acids. Suchprimary poly-silicates carry a number of free hydroxyl radicals whichbecause of their chemical position are capable of giving off hydrogenions. These hydroxyl radicals are believed to be responsible for thebleaching action of the clay, although the manner in which they exerttheir action is not altogether clear. Some investigators believe it tobe due to the hydrogen ions available from them while others assume aloose combination of said radicals with the coloring matter.

It is immaterial to my invention by what mechanism decolorization takesplace for in either case the hydroxyl radicals are responsible for it.Destroying, altering, or removing all or part of them will reduce theefllciency in direct proportion to the number removed or renderedineffective. For instance, the addition of alkali to activated clayslowersvtheir efliciency by converting the acid reacting hydroxylradicals to their alkali salt .of neutral or basic reaction.

If one considers the chemical structure of a typical aluminum silicate,which is believed to be one of the most common in activated bleachingclays, one can easily imderstand why drying such a clay may cause it tolose efllciency. For instance, the mono-aluminum salt of the disllicicacid has the following formula:

on el -on on o s on 0 on on A1-o -si- -on on o o si -on si-on on o si onAs will be noted, this compound has fifteen hydroxyl radicals threegroups of three, and three groups of two. It is a well known factthat tochemists that where there are two or more hy- 6 droxyl radicals groupedaround a single atom,

'16 ing compound:

From. this formula it will be observed that of the original fifteenradicals six are removed. or 40% of the total. If this formula iscorrect the eiliciency of this compound as compared with the originalcompletely hydrated one should be 60%.

As may be observed from the hereinbefore mentioned graph, themoisture-eillciency line goes through the 60% efliciency point for 0%mois- 1 ture. This represents a remarkable check.

The problem of drying acid activated clays in a manner which preservestheir eillciency resolves itself to the task of fractionating the waterof physical admixture from the water of chemical hydration. Water ofadmixture can be removed without affecting the eihciency of the claydown to a point at which its vapor pressure is equal to or lower thanthat of the water of hydration. Normally, admixed water has a .slightlyhigher vapor pressure than water of hydration but this difference is sosmall that attempts heretofore made to evaporate only the 60 admixedwater have caused a loss of hydroxyl radicals even when drying wascarried out at room temperatures.

I have discovered in accordance with and constituting a principalfeature of the present inventlon, that by exposing the clay tosuperheated steam, preferably at super-atmospheric pressures, a fairfractionation of the admixed from the combined moisture can be achieved.It has also been discovered that the temperature of the steam and itspressure must stand in a definite relation for optimum results. Thesteam should be at a temperature above that of its saturation point atthe existing pressure in the drying vessel by not more than about 50 F.,preferably less.

For example, activated Woodite clay pulp is deposited in a filter 'pressand then steam at a temperature of 270 F. is passed therethrough for aperiod of about 40 minutes under a back pressure of 16 pounds. At 16pounds pressure above atmospheric the temperature of saturated steam is252 F. Hence, thesteam in this example is superheated by 18 F. Clay thustreated has a moisture content of 20% and an emciency of 100% of theoriginal clay pulp,

It is not necessary that the steaming be ar.

rled out in a filter p ess, for although this is generally the mostconvenient way of "doing it,"

any apparatus in which the wet clay can be brought in thorough contactwith steam under the proper conditions is suitable.

Constituting a second feature of the present invention I have discoveredthat partially dehydrated clays of decreased eillciency can beregenerated to substantially their original eillciency. Dried clays thathave lost part of their sures reactivation can be effected but it takesplace at rates too slow to be of commercial importance. Saturated steamrevivifles. clays somewhat fasterthan slightly superheated steam, buthas the disadvantage of producing a clay product of high moisturecontent. The application of steamat 100 to 150 pounds-pressure attemperatures of from 2 to 10 1''. above its saturation point producessubstantially dry clays of high efilciency, within 15 to 40 minutes.

For example, dried activated Woodite" having a moisture content of 19%and an efliciency of 75% as compared with its original pulp is exposedfor 15 minutes to saturated steam of 110 pounds per square inch. Theresulting clay contains 30% moisture and has an efliciency of 95%.

Clays that have been over-dried", i. e., that have been dried under suchsevere conditions that they have an eiliciencylower than theirmoisture-efiiciency line indicates they should have. cannot altogetherbe revivifled by steam, possibly because of chemical changes otherithansimple dehydration which may have occurred during the drying process.Thus if a Woodite" clay having 73% efficiency and 20% moisture is giventhe same steam treatments, as the 19% moisture and 75% eillciency clayof the previous example, there results a product having an efficiency ofas against in the previous test. 1

In accordance with a third feature of the instant invention, I havediscovered that oils can be more efliciently decolorized where ordinarydried acid. activated clay is employed if steam. under a substantialsuper-atmospheric pressure is introduced into the mixture of oil. andclay while the temperature is gradually raised. In this case, the driedclay appears to be revivifled simultaneously with the decolorlzation ofthe oil. I have found that for economical performance steam pressures ofnot less than50 pounds per square inch should be applied. i

In my preferred procedure, I heat the mixture of dried activated clayand oil to about the boiling point of water or between about 200 to 250F., in a shell still or other suitable closed vessel in which a meanshas been provided for thorough agitation. Steam is then introduced untilthe pressure builds up to about pounds. The pressure is preferablymaintained by the introduction of additional steam, which introductionmay be regulated automatically. when the temperature for optimumdecolorization has been reached, which in the case of Woodite is around4 20 F., the pressure is released and the contacted batch of oilwithdrawn and separated from the clay in any suitable manner, as byfiltering. In

. increase the amount oi. physically admixed moisthis manner the oil isdecolorized without foaming or other objectionsv which arise with theuse of wet clay. Instead of shell stills, pipe stills can be used aswell, provided the oil and the clay mixture is thoroughly agitated andsteam is introduced during the heating and circulating period.

A dried activated Woodite" clay containing 19% moisture and having upondry contacting an efliciency of 75% had when employed as abovedescribed, an efliciency of 90%. If pressures as low as 20 pounds areemployed, absolutely no increase in efliciency is obtained.

It should be understood that I do not intend that the instant inventionbe limited to Wooditef clay only or to any special equipment describedor to any theory of operation set out herein. Other acid-activated clayssuch as California Palex" or FiltroP' etc., behave similarly to Woodite,except that their moisture-efllciency lines are somewhat different, andthat optimum conditions as to temperatures of contacting, minimumpressures required, reactivation, etc., differ slightly from theexamples cited. The instant invention is limited only by the scope ofthe appended claims.

Iclaim:

1. The process of drying acid-activated clay comprising treating thesame with superheated steam for a period of time sufilcient to reduce,the amount of physically admixed moisture to within a range of -20% 01the dried clay, but insufiicient to remove water of hydration.

2. The process of drying acid-activated clay comprising evaporating onlyphysically admixed water by treating the same with super-heated steamfor a period sumcient to reduce the amount of physically admixedmoisture to about 20% of the dried clay.

3. The process of drying acid-activated clay comprising evaporating onlythe physically admixed water by treating the same with super- 7 heatedsteam under super-atmospheric pressure.

4. The process of drying acid-activated clay comprising evaporating onlythe physically admixed water by treating the same with steam superheatedby not more than. 50 F.

5. The process of drying acid-activated clay comprising evaporating onlythe physically admixed water by treating the same with steam superheatedby not more than 50 F. under superatmospheric pressure.

6. A fully hydrated having from 20 to 50% ture.

'7. A washed partially dried containing less than 50% 20% of physicallyadmixed water having a. decolorizing eiilciency unimpaired by drying.

8. The process of producing acid-activated clay having less than 50%physically admixed moisture and having substantially all of its water ofhydration, from overdried acid-activated clay comprising treating suchclay with superheated steam under super-atmospheric pressure of at least50 lbs. for a period suiiicient to increase the amount of physicallyadmixed moisture to within a range of 20-50% of the dried clay.

washed acid-activated clay physically admixed mois-' acid-activated clay9. The process of raising the decolorizing emoverdried acid-activatedclay comprissteam under superperiod suficient to ciency of ing treatingthe same with atmospheric pressure for a and more than about ture towithin a range of 20-50% of the dried clay.

10. The process of raising the decolorizing emciency of overdriedacid-activated clay comprising treating the same with steam undersuperatmospheric pressure of at least 50 pounds for a superheated to adegree not in excess of 50 F.

12. The process 0! increasing the decolorlzlng efiiciency of overdriedacid-activated clay comprising treating the same with saturatedsteamfora period sufllcient to increase the amouhtmf physically admixed moistureto within a r go of 20-50% of the dried clay.

13. The process of increasing the decoloriz n-g? period suiflcient toincrease the amount of phys- 1 efficiency of overdried acid-activatedclay comprising treating the same, with saturated steam under asuper-atmospheric pressure for a period sufficient to increase theamount of physically admixed moisture to within a range of 20-50% of thedried clay.

14. The process of increasing the water of hydration content withoutincreasing the physically admixed water .to an objectionable extent, ofoverdried acid-activated clay comprising passing steam through a body ofsaid clay, under a super-atmospheric pressure of at least 50 pounds. fora period sufllcient to increase the amount of physically admixedmoisture to within a range of 20-50% of the dried clay.

15. The prodess of raising the decolorizing etficiency of overdriedacid-activated clay containing not more than about 50% moisture, and ofsimultaneously treating oil therewith comprising mixing oil to bedecolorized with such clay, heating the mixture, and introducing steamduring heating whereby a super-atmospheric pressure of not less than 50pounds is reached, said treatment to continue till decolorizing actionis complete.

16. The process of raising the decolorizing eii'iciency of overdriedacid-activated clay containing not more than about 50% moisture, and ofsimultaneously treating oil therewith comprising contacting oil to bepurified with such clay, introducing steam in the mixture andmaintaining a super-atmospheric pressure of about 50 lbs. per squareinch on saidmixture, whereby water of hydration is introduced into saidclay and said 011 is purified said treatment is continued untildecolorizing action is complete.

17. The process of decolorizing oil with overdried acid-activated claycontaining not more than about 50% moisture, comprising mixing oil andsuch clay, heating the mixture ,to a temperature above the boiling pointof water, introducing steam. maintaining a pressure of not less thanabout '50 pounds in the contacting zone,

raising the temperature of the mixture during- ERNEST W. ZUBLIN.

